Systems and methods for closed-loop recycling of a liquid component of a leaching mixture when recycling lead from spent lead-acid batteries

ABSTRACT

The present disclosure relates generally to systems and methods for recycling lead-acid batteries, and more specifically, relates to purifying and recycling the lead content from lead-acid batteries. A system includes a reactor that receives and mixes a lead-bearing material waste, a carboxylate source, and a recycled liquid component to form a leaching mixture yielding a lead carboxylate precipitate. The system also includes a phase separation device coupled to the reactor, wherein the phase separation device isolates the lead carboxylate precipitate from a liquid component of the leaching mixture. The system further includes a closed-loop liquid recycling system coupled to the phase separation device and to the reactor, wherein the closed-loop liquid recycling system receives the liquid component isolated by the phase separation device and recycles a substantial portion of the received liquid component back to the reactor as the recycled liquid component.

CROSS-REFERENCE

This application is a divisional application of U.S. application Ser.No. 14/498,798, entitled “SYSTEMS AND METHODS FOR CLOSED-LOOP RECYCLINGOF A LIQUID COMPONENT OF A LEACHING MIXTURE WHEN RECYCLING LEAD FROMSPENT LEAD-ACID BATTERIES”, filed Sep. 26, 2014, which claims priorityfrom and the benefit of U.S. Provisional Application Ser. No.62/015,045, entitled “METHODS FOR PURIFYING AND RECYLING LEAD FROM SPENTLEAD-ACID BATTERIES”, filed Jun. 20, 2014, U.S. Provisional ApplicationSer. No. 62/015,042, entitled “SYSTEMS AND METHODS FOR PURIFYING ANDRECYLING LEAD FROM SPENT LEAD-ACID BATTERIES”, filed Jun. 20, 2014, U.S.Provisional Application Ser. No. 62/015,058, entitled “SYSTEMS ANDMETHODS FOR CLOSED-LOOP RECYCLING OF A LIQUID COMPONENT OF A LEACHINGMIXTURE WHEN RECYCLING LEAD FROM SPENT LEAD-ACID BATTERIES”, filed Jun.20, 2014, U.S. Provisional Application Ser. No. 62/015,070, entitled“SYSTEMS AND METHODS FOR SEPARATING A PARTICULATE PRODUCT FROMPARTICULATE WASTE WHEN RECYCLING LEAD FROM SPENT LEAD-ACID BATTERIES”,filed Jun. 20, 2014, which are hereby incorporated by reference for allpurposes.

BACKGROUND

The present disclosure relates generally to systems and methods forrecycling lead-acid batteries, and more specifically, relates topurifying and recycling the lead content from lead-acid batteries.

The lead present in a lead-acid battery may be in a number of forms. Forexample, a lead-acid battery may include grids that contain lead alloysand lead oxide (PbO, PbO₂), battery paste that contains metallic leadsponge, lead oxide, red lead, and/or lead sulfate, and posts and/orinterconnects that contain metallic lead, lead alloys, and which mayalso contain non-lead alloys. While it may be desirable to attempt torecover lead from the waste of spent or retired lead-acid batteries,this material may include a variety of lead compounds (lead alloys,oxides, sulfates and carbonates) and an array of physical and/orchemical impurities. Existing methods for purifying lead typically relyalmost entirely on multi-stage pyrometallurgical smelting in which someof these compounds are combusted to produce volatile gases, some ofwhich must be scrubbed (e.g., captured and removed from the exhauststream) to prevent release, in accordance with environmentalregulations, and subsequently the remaining impurities are removed fromthe metallic lead in various refining operations. Since these operationsoften require specialized equipment and certain consumables (e.g.,solutions or other refining agents), this refinement process generallyadds cost and complexity to the lead recovery process.

SUMMARY

The present disclosure relates to systems and methods by which lead fromspent lead-acid batteries may be extracted, purified, and used in theconstruction of new lead-acid batteries. In an embodiment, a systemincludes a reactor that receives and mixes a lead-bearing materialwaste, a carboxylate source, and a recycled liquid component to form aleaching mixture yielding a lead salt precipitate. The system alsoincludes a phase separation device coupled to the reactor, wherein thephase separation device isolates the lead salt precipitate from a liquidcomponent of the leaching mixture. The system further includes aclosed-loop liquid recycling system coupled to the phase separationdevice and to the reactor, wherein the closed-loop liquid recyclingsystem receives the liquid component isolated by the phase separationdevice and recycles a substantial portion of the received liquidcomponent back to the reactor as the recycled liquid component.

In another embodiment, a method includes forming a leaching mixturehaving a lead-bearing material, a carboxylate source, and a recycledliquid component, wherein the leaching mixture generates a lead saltprecipitate as the carboxylate source reacts with the lead-bearingmaterial. The method also includes isolating a liquid component from thelead salt precipitate of the leaching mixture. The method furtherincludes recycling at least a portion of the isolated liquid componentback into the leaching mixture as the recycled liquid component.

In another embodiment, a system includes a closed-loop liquid recyclingsystem coupled to a leaching vessel that contains a leaching mixture.The liquid recycling system receives a liquid component of the leachingmixture, purifies the received liquid component to generate a purifiedliquid component having a lower sulfate content than the received liquidcomponent, and provides the purified liquid component to the leachingvessel as part of the leaching mixture.

DRAWINGS

FIG. 1 is a flow diagram illustrating an embodiment of a process bywhich lead from spent lead-acid batteries may be extracted, purified,and used in the construction of new lead-acid batteries; and

FIG. 2 is a schematic of an embodiment of a system for performing theprocess of FIG. 1.

DETAILED DESCRIPTION

One or more specific embodiments will be described below. In an effortto provide a concise description of these embodiments, not all featuresof an actual implementation are described in the specification. Itshould be appreciated that in the development of any such actualimplementation, as in any engineering or design project, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which may vary from one implementation toanother. Moreover, it should be appreciated that such a developmenteffort might be complex and time consuming, but would nevertheless be aroutine undertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments of the presentdisclosure, the articles “a,” “an,” and “the” are intended to mean thatthere are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.Additionally, it should be understood that references to “oneembodiment” or “an embodiment” of the present disclosure are notintended to be interpreted as excluding the existence of additionalembodiments that also incorporate the recited features.

As used herein, the disclosure of a particular component being made ofor including a particular element called out by name (e.g., lead),should be interpreted to encompass all forms of lead (e.g., metalliclead, lead compounds, or mixtures thereof). For distinction, as usedherein, the disclosure of a metallic form of an element may be indicatedby the chemical formula (e.g., Pb(0)) or using the terms elemental,metallic, or free (e.g., elemental lead, metallic lead, or free lead).As used herein, “leady oxide” may be used to indicate a mixture ofmetallic lead (e.g., Pb(0)) and lead oxide (e.g., PbO) in various ratiosas described. As used herein, the term “substantially free” may be usedto indicate that the identified component is not present at all, or isonly present in a trace amount (e.g., less than 0.1%, less than 0.01%,or less than 0.001%). As used herein, “an element or compound of GroupX” may refer to any chemical substance (e.g., element or compound) thatincludes an element from the identified column of the periodic table.For example, “an element or compound of Group 14” may include any of theelements from Group 14 (e.g., carbon, silicon, tin, etc.) as well as anycompounds that include Group 14 elements (e.g., carbonates, silicates,stannates, etc.). As used herein, a “carboxylate source” is any moleculeor polymer that includes at least one carboxylate or carboxylic acidmoiety or functionality. Accordingly, a non-limited list of examplecarboxylate sources include: citric acid, acetic acid, formic acid,citrate, acetate, formate, dilactate, oxalate, tartarate, or anycombination thereof. The term “citrate” herein refers to citric acid, ora citrate salt of a Group 1 or Group 2 metal, or ammonium citrate. Theterm “acetate” herein refers to acetic acid, or acetate salts of a Group1 or Group 2 metal, or ammonium acetate. “New lead-acid battery” hereinrefers to a newly produced lead acid battery, while the term “spentlead-acid battery” indicates a battery at the end of its useable servicelife. As used herein “peroxide” refers to hydrogen peroxide and/or anyorganic peroxide (e.g. peracetic acid). The term “hydroxide” hereinindicates a Group 1 or Group 2 metal hydroxide, ammonium hydroxide, orammonia gas introduced into the reaction mixture to form ammoniumhydroxide in-situ, or combinations thereof.

As mentioned above, existing methods typically rely heavily onpyrometallurgical smelting or combustion to recover and purify lead fromspent lead-acid batteries. For such methods, the lead-bearing materialfrom spent lead-acid batteries, which may include a number of leadcompounds and a number of impurities, may be heated such that at least aportion of the impurities may combust or volatilize and be released asbyproducts. Additionally, after pyrometallurgical smelting or combustionof the lead-bearing material, such methods may involve subsequentrefinement steps to remove byproducts or other impurities to yieldpurified lead. Since the atmospheric release of some of these combustionbyproducts (e.g., SO₂, soot) may be restricted by local environmentalregulations, present embodiments are directed toward enabling asolution-based removal of several impurities from the recovered lead,thereby avoiding or reducing the formation of such combustion byproductsand/or the cost associated with scrubbing them from the exhaust stream.Additionally, present embodiments address limitations of other wastelead purification techniques, enabling a robust technique for purifyingand recycling of recovered lead on an industrial scale. Moreover, asdiscussed in detail below, present embodiments enable the closed-looprecycling of the liquid component of the leaching solution used duringthe lead recovery and purification process, which both enhances leadrecovery and avoids potentially costly waste disposal of this liquidcomponent. Accordingly, present embodiments enable a lead recovery andpurification technique that is robust to the presence of a wide varietyof impurities, improves lead recovery, and limits the production ofbyproducts that may be costly to properly purify and discard.

FIG. 1 is a flow diagram illustrating an embodiment of a process 10 bywhich lead from spent lead-acid batteries may be extracted, purified,and used in the construction of new lead-acid batteries. It may beappreciated that the process 10 of FIG. 1 is merely provided as anexample and, in other embodiments, the process 10 may include additionalpurification steps (e.g., additional hydrometallurgical purificationsteps, additional phase-, size- or density-based separation steps,additional pH adjustment steps) in accordance with the presentdisclosure. As illustrated in FIG. 1, the process 10 begins with theprocessing (block 12) of spent lead-acid batteries to generate alead-bearing material. For example, in an embodiment, one or morelead-acid batteries may be fed through a hammer mill or another suitabledevice that is capable of crushing, pulverizing, grinding or otherwisephysically digesting the entirety of the spent lead-acid battery. Thecomponents of the spent lead-acid battery may include, for example,metal posts, metal connectors, metal grids, carbon black, glass, aplastic or metal casing, plastic separators, plastic fibers,lignosulphonates or other organic expanders, battery paste (e.g.,including various lead oxides, lead carbonates, lead sulfates), sulfuricacid, among other components (e.g., non-lead-based metal components,such as, brass terminals). The lead present in the spent lead acidbattery may be in a number of different forms, including, for example,PbO₂, PbO, PbSO₄, PbCO₃, and Pb(0).

After being substantially pulverized, the resulting battery waste may,in certain embodiments, be passed through one or more preliminarypurification steps in which certain components (e.g., the crushedplastic components) may be removed from the remainder of thelead-bearing mixture, for example, using a separation device (e.g., asettling tank or cyclone separator) that takes advantage of the lowerdensity of these plastic components. For example, in certainembodiments, sieving may be applied as a separation step to separatemassive metal particle fractions from other portions of the batterywaste. Further, in certain embodiments, some, or all, of the residualsulfuric acid entrained in the lead-bearing material may be recycled forreuse, or neutralized and crystallized as a solid sulfate for disposalor resale. In certain embodiments, pre-treatment of the lead-bearingmaterial may include a full or partial desulfurization stage in whichthe sulfate content of the lead-bearing material may be reduced bychemical means, for example, by treatment with a hydroxide (e.g., sodiumhydroxide) or carbonate (e.g., soda ash). Each of these actions or stepsmay be generally represented by block 12.

The illustrated method 10 continues with forming (block 14) a leachingmixture that includes the lead-bearing material generated in block 12(which may include all of the battery waste, or a separated fractionthereof, as discussed above), a carboxylate source, and a recycledliquid component. The recycled liquid component is or may be formed froman aqueous solution that is isolated during a later step (block 18) ofthe method 10, as discussed in greater detail below. In block 14, therecycled liquid component may be partially or entirely saturated with adissolved lead salt, (e.g., lead citrate, lead acetate, and/or otherlead salts), and may generally provide a medium for the leaching of thelead-bearing material. In certain embodiments, the carboxylate sourcemay be metal citrate (e.g., sodium citrate), citric acid, metal acetate(e.g., sodium acetate), acetic acid, a combination thereof, or any othersuitable carboxylate source that may drive the formation of lead saltsin the leaching mixture. In certain embodiments, water and/or peroxidemay be added to the leaching mixture as well to encourage thedissolution of solid lead and the formation of lead salts (e.g., leadcitrate, lead acetate) in the leaching mixture. In certain embodiments,sodium hydroxide or sodium carbonate may be added to the mixture, orsodium citrate may be used as at least a portion of the carboxylatesource, to encourage the formation of sodium sulfate from lead sulfatethat may be present in the leaching mixture.

In certain embodiments, block 14 may be performed in a reactor, such asa leaching tank, at low (acidic) pH (e.g., pH between 1 and 7) and atslightly elevated temperatures (e.g., approximately 30° C. or more). Itmay be appreciated that this leaching mixture may include both solubleand insoluble residuals from the spent and digested batteries.Additionally, the carboxylate source reacts with one or more forms oflead in the leaching mixture (e.g., metallic lead, lead sulfate, leadcarbonate, and lead oxide), with or without the assistance of aperoxide, to yield one or more lead salts. Since these lead salts mayhave limited solubility at low pH levels, a lead salt precipitate (e.g.,a lead citrate precipitate, a lead acetate precipitate) may be generated(block 16) in the leaching mixture as a result. Further, as discussedbelow, the lead salt dissolved in the recycled liquid component mayencourage the generated lead salt to precipitate within the leachingmixture.

Subsequently, the lead salt precipitate may be isolated (block 18) fromthe liquid component of the leaching mixture, for example, byfiltration. After being separated from the liquid component of theleaching mixture, the lead salt precipitate may be washed with water,and the filtrate and wash water may retain all or most of the remainingimpurities from the lead salt precipitate. For example, in certainembodiments, the isolated lead salt precipitate may include little or noresidual sulfates (e.g., sodium sulfate and/or lead sulfate), such asless than 5% sulfates, less than 4% sulfates, less than 3% sulfates,less than 2% sulfates, less than 1% sulfates, less than 0.5% sulfates,less than 0.3% sulfates, or less than 0.1% sulfates. Recycling of theliquid component (and the wash-water) is discussed in greater detailbelow.

Next in the illustrated process 10, the lead salt precipitate may betreated (block 20) to yield leady oxide. For example, in certainembodiments, the treatment of block 20 may involve treating the isolatedlead salt precipitate with base (e.g., hydroxide, 25-50 wt % sodiumhydroxide solution) to yield the leady oxide product. In certainembodiments, the treatment of block 20 may involve a calcinationtreatment performed using a belt-dryer, a spray calciner, a stirred potreactor, a rotary kiln, or another suitable calciner or kiln. Forembodiments utilizing a calcination treatment, the lead salt precipitatemay be heated to a temperature less than 450° C. (e.g., betweenapproximately 275° C. and approximately 400° C., at approximately 330°C.). In certain embodiments, this heating may occur in the presence of agas stream (e.g., air, oxygen-enriched air, oxygen-reduced air,air/inert gas mixtures, water steam) such that the organic portion ofthe carboxylate source combusts, resulting in a mixture of free lead(i.e., Pb(0)) and lead oxide (i.e., PbO), generally referred to as leadyoxide. Since the carboxylate source structure includes a substantialamount of oxygen, in certain embodiments calcination may occur whilecombusting an oxygen reducer (e.g., methane, coke, propane, natural gas,etc.) to limit the amount of oxygen present during the calcinationprocess to control the chemistry of the leady oxide product. For suchembodiments, examples of process controls that may affect the resultingleady oxide include the temperature of the calcination, time, dropletsize (e.g., for spray calcination), lead salt particle size, how muchresidual water remains in the lead salt, the rate at which the lead saltis heated to the calcination temperature, and/or oxygen content in thegas stream.

The illustrated process 10 continues with the leady oxide produced fromthe treatment of block 20 being formed (block 22) into a leady oxideactive material for use in new lead-acid batteries. For example, theleady oxide may be mixed with water and sulfuric acid to form a batterypaste that may be applied to a plurality of lead grids to serve as theactive material of a new lead-acid battery. Accordingly, a new lead-acidbattery may be constructed (block 24) using the leady oxide batterypaste formed in block 22. The leady oxide active material formed by thepresent approach may enable the production of new lead-acid batterieshaving good to excellent electrical performance. The leady oxide formedin block 20 may also be used to manufacture tribasic lead sulfate (3BS),tetra basic lead sulfate (4BS), and red lead (lead (II,IV) oxide,Pb₃O₄). In the case of 3BS and 4BS, the materials may be produced bymixing the leady oxide formed in block 20 with water and sulfuric acidusing a mixer. In the case of red lead, the material may be formed byfurther treating (e.g., calcining and/or oxidizing) the leady oxideformed in block 20. All of these materials are useful in theconstruction of new lead-acid batteries, or for other suitable technicalpurposes.

Further, it may be appreciated that, while the isolated liquid componentof the leaching mixture, as well as any water washes, contain certaincontaminants (e.g., sulfates or salts of elements other than lead) thatare desirably separated from the lead salt precipitate in block 18, thisisolated liquid component also includes a substantial amount ofdissolved lead salt. That is, while the solubility of the lead salt inthe leaching mixture of block 16 may be low (e.g., due to the pH of theleaching mixture and/or the amount of lead salt present in the leachingmixture), a certain amount of lead salts (e.g., lead citrate, leadacetate) will remain dissolved in the liquid component after the leadsalt precipitate is isolated in block 18. Indeed, in certainembodiments, this isolated liquid component may be partially orcompletely saturated with lead salt (e.g., at least 5% saturated, atleast 10% saturated, or at least 15% saturated with lead salts, up to100% saturated in lead salts) and may also include other impurities(e.g., lead sulfate, sodium sulfate, or other salts of elements otherthan lead). As such, if the liquid component were to be discarded, asubstantial amount of purification (e.g., lead removal, sulfate removal,etc.) would likely be performed, and a substantial amount of lead wouldbe lost as well. By recycling the isolated liquid component back intothe leaching mixture in block 14 in a closed-loop manner, theaforementioned high concentration of dissolved lead salt (e.g., leadcitrate, lead acetate) in this recycled liquid component encourages theadditional lead salt generated in block 16 to precipitate, rather thanremaining dissolved in the leaching mixture. Accordingly, in addition toavoiding costly purification and disposal steps, the presently disclosedrecycling of the liquid component of the leaching mixture increases theyield of the lead salt precipitate isolated in block 18 and the overallefficiency of the method 10.

With the foregoing in mind, the method 10 illustrated in FIG. 1 includessteps whereby the liquid component isolated in block 18 may be recycledback into the leaching mixture of block 14, limiting the production ofwaste and improving lead recovery. As illustrated in FIG. 1, the liquidcomponent isolated in block 18, which may or may not include the waterfrom one or more washes, may be purified (block 26) to remove one ormore impurities from the liquid component before the liquid component isrecycled (block 28) into the mixture of block 14. For example, incertain embodiments, it may be desirable to remove or reduce the sulfatecontent (e.g., sodium sulfate, lead sulfate, salts of elements otherthan lead, etc.) in the liquid component before it is recycled back intothe leaching mixture of block 14. By specific example, in certainembodiments, the purification of block 26 may include a chemicalpurification (e.g., forming insoluble calcium sulfate from othersulfates using calcium hydroxide), physical purification (e.g., reverseosmosis or nanofiltration), and/or ion exchange resins. It may beappreciated that, in certain embodiments, the purification described byblock 26 preferably removes the one or more impurities from the liquidcomponent without substantially altering the amount of lead salt (e.g.,lead citrate, lead acetate) dissolved in the liquid component. Further,in certain embodiments, the liquid component isolated in block 18 doesnot receive the purification described by block 26 and may, instead, bedirectly recycled (block 28) into the leaching mixture of block 14.

FIG. 2 illustrates an embodiment of a system 40 configured to performthe process illustrated in FIG. 1 in what may be referred to as acontinuous manner. In certain embodiments, some or all of theillustrated system 40 may be implemented as a multi-stage reactorsystem, or a series of individual reactors and devices, to enable thecontinuous processing of spent lead-acid batteries into leady oxideparticles. In addition to these devices, stages, and/or reactors(illustrated as rectangles) in the system 40, FIG. 2 also illustratesthe various inputs and outputs (illustrated as non-rectangularparallelograms) for each device in the system 40. The illustrated system40 of FIG. 2 has a control system 42 that includes a controller 44(e.g., a programmable logic controller (PLC)). The controller 44includes a memory 46 and a processor 48, which enable the controller 44to store and execute instructions (e.g., applications, modules, apps,firmware) to control operation of the system 40 via field devices 49.For examples, field devices 49 may include any number of sensing devices(e.g., temperature sensors, pressure sensors, flow rate sensors, oxygensensors, particle size sensors, rotational speed sensors, pH sensors)that are disposed throughout the system 40 and are communicativelycoupled to the controller 44 (e.g., via a wired or wirelesscommunication channel) to enable the controller 44 to determine theoperational parameters of the system 40. Further, the field devices 49may include any number of control devices (e.g., actuators, valves,motors, pumps, screws, heating elements, compressors) configured toreceive control signals from the controller 44 and modulate theoperation or state of the system 40 accordingly.

With the foregoing in mind, the illustrated system 40 includes alead-acid battery processing system 52 that receives spent lead-acidbatteries 50 and generates a lead-bearing material 54. As such, thelead-acid battery processing system 52 performs the acts described byblock 12 of the process 10 illustrated in FIG. 1. As mentioned above,this lead-acid battery processing system 52 may include a hammer mill oranother suitable device that is capable of receiving entire lead-acidbatteries (e.g., via a feed chute) and grinding the lead-acid batteriesinto particulate battery waste. Additionally, as mentioned above, thelead-acid battery processing system 52 may include some preliminarypurification features to remove one or more components from theresulting battery waste. For example, in certain embodiments, thelead-acid battery processing system 52 may include a cyclone separationdevice that receives the particulate battery waste exiting the hammermill, and may separate lower density battery waste (e.g., plasticcomponents from the housing of the lead-acid batteries) from thehigher-density lead-bearing material 54, which may subsequently beadvanced to the next device (e.g., leaching vessel 56) in theillustrated system 40. Also, as mentioned above, sieving may be appliedto separate massive metal particle fractions from other fractions of thebattery waste.

The system 40 illustrated in FIG. 2 includes a leaching vessel 56 thatis configured to perform the acts described in blocks 14 and 16 of theprocess 10 illustrated in FIG. 1. The leaching vessel 56 may be areactor or a stage of a multi-stage reactor (e.g., a leaching tank orreactor) that receives the lead-bearing material 54 from the lead-acidbattery processing system 52 and adds a carboxylate source 58 (e.g.,citric acid, sodium citrate, acetic acid, sodium acetate, or acombination thereof) and a purified, recycled liquid component 60 (e.g.,a solution that is at least partially saturated in lead salts) to form aleaching mixture 62. In certain embodiments, the leaching vessel 56 mayalso add a peroxide, a hydroxide, acetic acid, and/or sodium carbonateto the leaching mixture 62 to drive the formation of lead salt from thelead-bearing material. In certain embodiments, the leaching vessel 56may also be capable of both providing temperature control (e.g., heatingand/or cooling to between approximately 30° C. to 100° C.) and agitation(e.g., mixing and/or stirring) of the mixture to facilitate formation ofthe lead salt precipitate in the leaching mixture 62. Accordingly, theleaching vessel 56 may produce (e.g., store, contain, or output) theleaching mixture 62, which includes the formed lead salt precipitate andthe remainder of the lead-bearing material. This leaching mixture 62 maysubsequently be advanced to the next device (e.g., phase separationdevice 64) in the illustrated system 40.

The system 40 illustrated in FIG. 2 includes a phase separation device64 that is configured to perform the acts described in block 18 of theprocess 10 illustrated in FIG. 1. In certain embodiments, the phaseseparation device 64 may include a filter press, a clarifier, a cycloneseparator, a settling tank, a belt dryer, or any other device capable ofseparating components of the leaching mixture 62 based on phase,density, and/or size. As such, the phase separation device 64 receivesthe leaching mixture 62 and separates the solid lead salt precipitate 66from the liquid component 68. Subsequently, the isolated lead saltprecipitate 66 may advance to the next device (e.g., lead saltprecipitate treatment device 70) in the illustrated system 40 andeventually provide the leady oxide particles 74, as discussed below.

For the illustrated embodiment, the liquid component 68 isolated by thephase separation device 64, which includes dissolved lead salt as wellas dissolved impurities (e.g., lead sulfate, sodium sulfate, salts ofelements other than lead), is subsequently delivered to the purificationdevice 76 of the closed-loop liquid recycling system 77. Thepurification device 76 is configured to perform the acts described inblock 26 of the process 10 illustrated in FIG. 1. By specific example,in certain embodiments, the purification device 76 may include a reactorthat adds calcium hydroxide to the liquid component 68, and a phaseseparation device (e.g., a filter press, a clarifier, a settling tank)that removes the resulting insoluble calcium sulfate the liquidcomponent 68 to produce (e.g., store, contain, or output) the purifiedliquid component 60. In other embodiments, the purification device 76may include a nanofiltration device and/or one or more ion exchangeresins to facilitate the removal of one or more impurities (e.g.,sulfates) from the liquid component 68 to produce (e.g., store, contain,or output) the purified liquid component 60 having substantially lesssulfates. Subsequently, the purified liquid component 60, still at leastpartially (e.g., at least 10%) saturated in lead salts, may be recycledinto the leaching mixture 62 within the leaching vessel 56. It may alsobe appreciated that, in other embodiments, the closed-loop liquidrecycling system 77 may not include the purification device 76 (or maybypass the purification device 76) and the liquid component 68 isolatedby the phase separation device 64 may be directly recycled back into theleaching mixture 62 within the leaching vessel 56 without purification.It may be appreciated that recycling the liquid component in aclosed-loop manner, as presently illustrated, reduces or eliminatesadditional purification and disposal steps while increasing the leadrecovery of the system 40.

The system 40 illustrated in FIG. 2 includes a lead salt precipitatetreatment device 70 that is configured to perform the acts described inblock 20 of the process 10 illustrated in FIG. 1. In certainembodiments, the lead salt precipitate treatment device 70 may include areactor that mixes the isolated lead salt precipitate 66 with base 86(e.g., a hydroxide, 25-50 wt % sodium hydroxide solution) to yield theleady oxide product 74. In certain embodiments, the lead saltprecipitate treatment device 70 may be a calciner (e.g., a belt dryer, abatch calciner, an oven, a spray calciner, a rotary kiln calciner, aspray pyrolysis reactor, a stirred pot reactor, or another suitablecalcination device). As such, the lead salt precipitate treatment device70 receives the lead salt precipitate 66 isolated by the phaseseparation device 64 and reacts the lead salt precipitate 66 with a gasstream (e.g., air, oxygen-enriched air, oxygen-reduced air, nitrogen/airmixtures, water steam) or base 72 (e.g., hydroxide) to form leady oxideparticles 74. For example, in certain embodiments, the lead saltprecipitate treatment device 70 may calcine the lead salt precipitate 66in a mixture of air and an oxygen-reducing agent (e.g., carbon basedmaterials such as methane, coke, propane, natural gas, etc.) to providean oxygen-poor environment to calcine the lead salt precipitate 66 intothe desired leady oxide product 74. The leady oxide particles 74 maysubsequently be used to form a leady oxide active material for theconstruction of new lead-acid batteries (e.g., as discussed in blocks 22and 24 of the process 10 in FIG. 1). As mentioned above with respect tothe process 10, the leady oxide produced by the illustrated system 40enables the production of new lead-acid batteries having good toexcellent electrical performance.

One or more of the disclosed embodiments, alone or on combination, mayprovide one or more technical effects useful in the recovery of leadfrom spent lead-acid batteries. Embodiments of the present approachenable the industrial scale extraction and purification of lead fromspent lead-acid batteries. Further, present embodiments enable theremoval of several impurities (e.g., insoluble impurities, sulfates,alloying metals) from the recovered lead, thereby avoiding or reducingthe formation of certain undesired combustion byproducts as well as thecost associated with scrubbing these byproducts from the exhaust stream.Accordingly, present embodiments enable continuous lead purificationtechniques that are robust to the presence of a wide variety ofimpurities and provide enhanced control over the parameters of thepurification process. Moreover, present embodiments enable the recyclingof the liquid component of the leaching mixture during the lead recoveryand purification process, which both enhances lead recovery and avoidspotentially costly waste disposal. The technical effects and technicalproblems in the specification are exemplary and are not limiting. Itshould be noted that the embodiments described in the specification mayhave other technical effects and can solve other technical problems.

While only certain features and embodiments of the disclosure have beenillustrated and described, many modifications and changes may occur tothose skilled in the art (e.g., variations in sizes, dimensions,structures, shapes and proportions of the various elements, values ofparameters (e.g., temperatures, pressures), mounting arrangements, useof materials, colors, orientations) without materially departing fromthe novel teachings and advantages of the subject matter recited in theclaims. The order or sequence of any process or method steps may bevaried or re-sequenced according to alternative embodiments. It is,therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the true spiritof the disclosure. Furthermore, in an effort to provide a concisedescription of the exemplary embodiments, all features of an actualimplementation may not have been described (i.e., those unrelated to thepresently contemplated best mode of carrying out the invention, or thoseunrelated to enabling the claimed invention). It should be appreciatedthat in the development of any such actual implementation, as in anyengineering or design project, numerous implementation specificdecisions may be made. Such a development effort might be complex andtime consuming, but would nevertheless be a routine undertaking ofdesign, fabrication, and manufacture for those of ordinary skill havingthe benefit of this disclosure, without undue experimentation.

1. A system, comprising: a reactor that receives and mixes lead-bearingmaterial, a carboxylate source, and a recycled liquid component to forma leaching mixture yielding a lead carboxylate precipitate; a phaseseparation device coupled to the reactor, wherein the phase separationdevice isolates the lead carboxylate precipitate from a liquid componentof the leaching mixture; and a closed-loop liquid recycling systemcoupled to the phase separation device and to the reactor, wherein theclosed-loop liquid recycling system receives the liquid componentisolated by the phase separation device and recycles a substantialportion of the received liquid component back to the reactor as therecycled liquid component.
 2. The system of claim 1, wherein theclosed-loop liquid recycling system comprises a purification device thatremoves at least one impurity from the received liquid component beforerecycling.
 3. The system of claim 2, wherein the at least one impuritycomprises dissolved sulfates.
 4. The system of claim 2, wherein the atleast one impurity comprises one or more elements other than lead. 5.The system of claim 4, wherein the one or more elements comprise sodium,barium, calcium, antimony, arsenic, tin, or combinations thereof.
 6. Thesystem of claim 2, wherein the purification device comprises: anotherreactor that mixes calcium hydroxide with the received liquid component;and another phase separation device that subsequently removes aresulting calcium sulfate precipitate from the received liquid componentbefore recycling.
 7. The system of claim 2, wherein the purificationdevice comprises a nanofilter or ion exchange resin.
 8. The system ofclaim 2, wherein a dissolved lead carboxylate content of the liquidcomponent is substantially the same before and after the purificationdevice removes the at least one impurity.
 9. The system of claim 1,wherein the carboxylate source comprises citric acid, a salt of citricacid, acetic acid, a salt of acetic acid, or a combination thereof. 10.The system of claim 1, wherein the recycled liquid component is asolution at least 10% saturated in dissolved lead carboxylate.
 11. Thesystem of claim 1, wherein the closed-loop liquid recycling systemreceives wash water along with the liquid component from the phaseseparation device and recycles the wash water along with the liquidcomponent.
 12. The system of claim 1, wherein the phase separationdevice comprises a belt dryer, a filter press, a clarifier, or a cycloneseparator.
 13. The system of claim 1, comprising a lead-acid batteryprocessing device that is configured to receive at least one lead-acidbattery and grind the at least one lead-acid battery into thelead-bearing material.
 14. The system of claim 1, comprising a leadcarboxylate precipitate treatment device that is configured to receivethe lead carboxylate precipitate isolated by the phase separation deviceand treat the lead carboxylate precipitate to form leady oxide.
 15. Thesystem of claim 14, wherein the lead carboxylate precipitate treatmentdevice comprises a belt dryer, a spray calciner, a stirred pot reactor,a rotary kiln calciner.
 16. A system, comprising: a closed-loop liquidrecycling system coupled to a leaching vessel containing a leachingmixture, wherein the closed-loop liquid recycling system receives aliquid component of the leaching mixture, purifies the received liquidcomponent to generate a purified liquid component having a lower sulfatecontent than the received liquid component, and provides the purifiedliquid component to the leaching vessel as part of the leaching mixture.17. The system of claim 16, comprising a phase separation device coupledto the leaching vessel and the closed-loop liquid recycling system,wherein the phase separation device receives the leaching mixture,including the liquid component, from the leaching vessel, isolates alead carboxylate precipitate from the liquid component of the leachingmixture, and provides the liquid component to the closed-loop liquidrecycling system.
 18. The system of claim 16, comprising the leachingvessel that, during operation, receives and mixes a lead-bearingmaterial, a carboxylate source, and the purified liquid component toform the leaching mixture.
 19. The system of claim 16, wherein thepurified liquid component includes substantially the same amount ofdissolved lead carboxylate as the received liquid component.
 20. Thesystem of claim 16, wherein the leaching mixture comprises: water, alead-bearing material, a carboxylate source, dissolved lead carboxylate,and a lead carboxylate precipitate.
 21. The system of claim 20, whereinthe carboxylate source comprises citric acid, a metal citrate salt,acetic acid, a metal acetate salt, or a combination thereof.
 22. Thesystem of claim 20, wherein the leaching mixture comprises a peroxide.23. The system of claim 20, wherein the leaching mixture comprisesacetate from acetic acid or from a metal acetate.